 /*******************************************************************************
  * Copyright (c) 2000, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.ui.part;

 import java.io.ByteArrayInputStream ;
 import java.io.ByteArrayOutputStream ;
 import java.io.DataInputStream ;
 import java.io.DataOutputStream ;
 import java.io.IOException ;

 import org.eclipse.swt.dnd.ByteArrayTransfer;
 import org.eclipse.swt.dnd.TransferData;

 /**
  * This class can be used to transfer an instance of <code>PluginTransferData</code>
  * between two parts in a workbench in a drop and drop operation.
  * <p>
  * In every drag and drop operation there is a <code>DragSource</code> and
  * a <code>DropTarget</code>. When a drag occurs a <code>Transfer</code> is
  * used to marshall the drag data from the source into a byte array. If a drop
  * occurs another <code>Transfer</code> is used to marshall the byte array into
  * drop data for the target.
  * </p><p>
  * A <code>PluginTransferData</code> contains the id of a drop action extension.
  * If a drop occurs the extension is invoked to perform a drop action. As a benefit,
  * the destination viewer doesn't need to have any knowledge of the items being
  * dropped into it.
  * </p><p>
  * This class can be used for a <code>Viewer<code> or an SWT component directly.
  * A singleton is provided which may be serially reused (see <code>getInstance</code>).
  * It is not intended to be subclassed.
  * </p>
  *
  * @see org.eclipse.jface.viewers.StructuredViewer
  * @see org.eclipse.swt.dnd.DropTarget
  * @see org.eclipse.swt.dnd.DragSource
  */
 public class PluginTransfer extends ByteArrayTransfer {

     private static final String TYPE_NAME = "pluggable-transfer-format";//$NON-NLS-1$

     private static final int TYPEID = registerType(TYPE_NAME);

     /**
      * Singleton instance.
      */
     private static PluginTransfer instance = new PluginTransfer();

     /**
      * Creates a new transfer object.
      */
     private PluginTransfer() {
         super();
     }

     /**
      * Returns the singleton instance.
      *
      * @return the singleton instance
      */
     public static PluginTransfer getInstance() {
         return instance;
     }

     /* (non-Javadoc)
      * Method declared on Transfer.
      */
     protected int[] getTypeIds() {
         return new int[] { TYPEID };
     }

     /* (non-Javadoc)
      * Returns the type names.
      *
      * @return the list of type names
      */
     protected String [] getTypeNames() {
         return new String [] { TYPE_NAME };
     }

     /* (non-Javadoc)
      * Method declared on Transfer.
      */
     protected void javaToNative(Object data, TransferData transferData) {
         PluginTransferData realData = (PluginTransferData) data;
         if (data == null) {
             return;
         }
         try {
             ByteArrayOutputStream out = new ByteArrayOutputStream ();
             DataOutputStream dataOut = new DataOutputStream (out);
             dataOut.writeUTF(realData.getExtensionId());
             dataOut.writeInt(realData.getData().length);
             dataOut.write(realData.getData());
             dataOut.close();
             super.javaToNative(out.toByteArray(), transferData);
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

     /* (non-Javadoc)
      * Method declared on Transfer.
      */
     protected Object nativeToJava(TransferData transferData) {
         try {
             byte[] bytes = (byte[]) super.nativeToJava(transferData);
             ByteArrayInputStream in = new ByteArrayInputStream (bytes);
             DataInputStream dataIn = new DataInputStream (in);
             String extensionName = dataIn.readUTF();
             int len = dataIn.readInt();
             byte[] pluginData = new byte[len];
             dataIn.readFully(pluginData);
             return new PluginTransferData(extensionName, pluginData);
         } catch (IOException e) {
             e.printStackTrace();
         }
         //can't get here
 return null;
     }
 }

